Activated carbon fiber and preparation method therefor

ABSTRACT

Disclosed is an activated carbon fiber, more specifically, a filament-type activated carbon fiber that is manufactured by activating a filament-type precursor fiber for the activated carbon fiber and has a strength of 0.01 to 1.0 g/denier so as to have improved durability.

TECHNICAL FIELD

The present invention relates to an activated carbon fiber used in woven fabrics and knitted fabrics, and a method of manufacturing the same.

BACKGROUND ART

Cotton, viscose rayon, polyacrylonitrile, pitch, or phenolic staple fibers are activated for use as well-known activated carbon fibers. However, such staple fibers include short fibers of 1 to 6 mm. Accordingly, free shrinkage occurs during a high-temperature heat treatment process, which is required for activation, and the staple fibers have excellent durability compared to powder- or granule-based activated carbon. However, the strength of activated carbon fibers is low. Therefore, most activated carbon fiber is easily worn when in use, to thus be converted into powder.

Recently, the purpose of activated carbon fibers has continuously expanded. Particularly, activated carbon fibers have a high distribution of micro-pores, which have a diameter of 10 to 20 Å, thus having excellent ability to treat SOx or NOx, thereby exhibiting excellent atmospheric cleanup ability. Accordingly, activated carbon fibers have been applied to road barriers and to chemical, biological, and radiological protectors.

However, in order to apply the fibers to road barriers or chemical, biological, and radiological protectors, the fibers must be reused, rather than being discarded after a single use. However, the micro-pores may easily break due to the weak structure of the staple fibers, and the fibers are not capable of being made reusable using a process such as simple washing.

Meanwhile, activated carbon fibers are manufactured using cellulose-based fibers, acrylonitrile-based fibers, phenolic fibers, pitch-based fibers, or polyvinyl alcohol-based fibers, depending on the material thereof. However, currently, cellulose-, PAN (polyacrylonitrile)-, and pitch-based carbon fibers are mainly manufactured, for reasons related to productivity and economic feasibility.

Natural cellulose fibers, such as arboreous cotton, hemp, and flax, pulp fibers, which are obtained from wood and bamboo, and regenerated cellulose fibers, such as viscose rayon and polynosic, are used as the raw material of cellulose-based activated carbon fibers. 0.5 to 20 wt % of a phosphorus compound is attached to or contained in the raw material of cellulose fibers. The resulting material is heat-treated in an inactivated state at a low temperature of 200 to 350° C., so that the reduction ratio of the cellulose fibers is 40 to 70% and the persistence rate of phosphorus is 70% or more, and further heat-treated in the atmosphere, which contains 5 vol % or more of steam, at 450 to 1,000° C., so that the reduction ratio of the cellulose-based fibers is 65 to 95% and the persistence rate of phosphorus is 10% or less, to thus be activated, thereby manufacturing activated carbon fibers having high adsorption ability.

Polyacrylonitrile (PAN), which is the raw material of acrylonitrile-based activated carbon fibers, is oxidized in an oxidative atmosphere until a saturated oxygen combination amount is 80% or more, and is then activated so as to manufacture activated carbon fibers.

Novolac fibers, as an aldehyde group, are uniformly cured to manufacture cured novolac fibers or cured novolac fiber structures, and the cured novolac fibers or cured novolac fiber structures are calcined in a mixed gas atmosphere of 10 to 49 vol % of steam and 90 to 51 vol % of inactive gas while the temperature is increased from 250° C. to 700° C. at a heating rate of 200 to 2,000° C./hr to manufacture phenolic activated carbon fibers.

Coal-based pitch, petroleum-based pitch (including natural or artificial asphalt), pitch or synthetic resins, which are generated as by-products in various organic synthesis and petroleum chemical industries, or pitch obtained through dry distillation of natural resins, is applied to be molded into fibers, and the pitch-based fibers are heat-treated in an oxidizing gas-containing atmosphere at 50 to 400° C. so as to undergo incompatible treatment and are then activated in an ammonia-containing atmosphere, thereby manufacturing pitch-based activated carbon fibers.

Polyvinyl alcohol-based fibers (PVA), to which a dehydrating agent is attached or which contain a dehydrating agent, are heated so that the weight of the fibers is reduced by 35% or more, and are subjected to a process of causing dehydration and carbonization reactions to form carbonaceous fibers and to a process of activating the carbonaceous fibers at a high temperature of 800 to 1,200° C. with high humidity in the presence a small amount of oxygen, thereby manufacturing polyvinyl alcohol-based activated carbon fibers.

In this regard, the yield of the activated carbon fibers may change depending on the carrier gas or steam, but is 50% for polyacrylonitriles and 20% for celluloses, such as viscose rayon or cotton, and phenols, which are considered to be low.

The activated carbon fibers including the aforementioned various materials are made of staple fiber-type materials, and various forms, such as paper, woven fabrics, and felt, may be obtained using the activated carbon fibers which are manufactured using the staple fibers.

However, activated carbon fibers manufactured using the staple fiber-type material have limited durability.

DISCLOSURE Technical Problem

Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide an activated carbon fiber having improved durability and a method of manufacturing the same.

Another object of the present invention is to provide a woven fabric or a knitted fabric which is manufactured using an activated carbon fiber having improved durability.

Technical Solution

In order to accomplish the above objects, the present invention provides a filament-type activated carbon fiber that is manufactured by activating a filament-type precursor fiber for the activated carbon fiber and has a strength of 0.01 to 1.0 g/denier.

The filament-type precursor fiber for the activated carbon fiber may be selected from the group consisting of a cellulose-based filament-type precursor fiber, a polyacrylonitrile-based filament-type precursor fiber, and an aramid-based filament-type precursor fiber.

The filament-type precursor fiber may have a strength of 5 to 12 g/denier.

The filament-type precursor fiber may have a single-yarn fineness of 0.05 to 10 denier and a total fineness of 300 to 30,000 denier.

In order to accomplish the above objects, the present invention also provides a method of manufacturing an activated carbon fiber. The method includes (S1) stabilizing a filament-type precursor fiber, and (S2) activating the filament-type precursor fiber by carbonizing the stabilized filament-type precursor fiber in an inactive atmosphere.

The method may further include precipitating the filament-type precursor fiber in an alkali solution before step (S1), and the filament-type precursor fiber may be a cellulose-based filament-type precursor fiber or an aramid-based filament-type precursor fiber.

The method may further include drying the filament-type precursor fiber before step (S1), the method may further include precipitating the filament-type precursor fiber in an alkali solution before drying it, and the filament-type precursor fiber may be a polyacrylonitrile-based filament-type precursor fiber.

The stabilizing of step (S1) may be performed using heat treatment in an inactive atmosphere at a temperature of 200 to 350° C. for 10 to 240 min when the filament-type precursor fiber is a cellulose-based filament-type precursor fiber or an aramid-based filament-type precursor fiber, and using heat treatment in ambient air at a temperature of 200 to 300° C. for 30 to 240 min when the filament-type precursor fiber is a polyacrylonitrile-based filament-type precursor fiber.

The activating of step (S2) may be performed at a temperature of 650 to 1,050° C. after low-temperature carbonization in the inactive atmosphere at the temperature of 300 to 500° C. for 1 to 30 min when the filament-type precursor fiber is a cellulose-based filament-type precursor fiber or an aramid-based filament-type precursor fiber, and at a temperature of 650 to 1,050° C. after high-temperature carbonization in an inactive atmosphere at a temperature of 500 to 950° C. for 1 to 30 min when the filament-type precursor fiber is a polyacrylonitrile-based filament-type precursor fiber.

The alkali solution may be selected from the group consisting of a phosphoric acid aqueous solution, an ammonium phosphate aqueous solution, and a zinc chloride aqueous solution.

The drying may be performed using heat treatment at a temperature of 100 to 150° C.

In order to accomplish the above objects, the present invention also provides a woven fabric manufactured using the activated carbon fiber.

In order to accomplish the above objects, the present invention also provides a knitted fabric manufactured using the activated carbon fiber.

Advantageous Effects

According to the present invention, activated carbon fiber having improved durability may be manufactured using a filament-type precursor fiber, and a woven fabric and a knitted fabric may be manufactured using the activated carbon fiber.

BEST MODE

Hereinafter, the present invention will be described in detail.

The present invention relates to an activated carbon fiber that is manufactured using a filament-type precursor fiber, which is a long fiber type, so as to have improved durability.

The activated carbon fiber is a filament-type activated carbon fiber, which is manufactured by activating a filament-type precursor fiber for the activated carbon fiber, and may have a strength of 0.01 to 1.0 g/denier.

In the present invention, the filament-type precursor fiber is used as the precursor fiber for the activated carbon fiber, which is used to manufacture the activated carbon fiber, so as to enable the activated carbon fiber to have excellent durability.

Further, the mechanical properties of the precursor fiber for the activated carbon fiber must be excellent. Specifically, the filament-type precursor fiber may have a strength of 3 to 30 g/denier. When the strength is less than 3 g/denier, the strength of yarn, which remains during an activation process performed to manufacture the activated carbon fiber, may be reduced to 0.01 g/denier or less, and accordingly, activated carbon fiber having excellent durability is not capable of being manufactured. Further, when the strength of the filament-type precursor fiber is more than 30 g/denier, since the precursor fiber must have a very high elongation ratio, the production yield of the precursor fiber is decreased, thus deteriorating economic feasibility.

Naturally, the degree of yarn orientation of the precursor is high enough to form micro-pores, but the substantial micro-pore area (BET) is very small in consideration of the heat treatment temperature. Accordingly, the filament-type precursor fiber may be used for the purposes of air pollution cleanup, gas purification and water treatment, but has a problem in that the amount of activated carbon fiber that is required in order to purify water is increased due to the relatively small micro-pore area (BET).

The filament-type precursor fiber for the activated carbon fiber may be selected from the group consisting of a cellulose-based filament-type precursor fiber, a polyacrylonitrile-based filament-type precursor fiber, and an aramid-based filament-type precursor fiber.

Further, the precursor fiber for the activated carbon fiber may have single-yarn fineness of 0.05 to 10 denier and overall fineness of 300 to 30,000 denier. When the single-yarn fineness of the activated carbon fiber is less than 0.05 denier or more than 10 denier, the weight of the yarns of the precursor fiber is reduced by 50 to 90% after activation, resulting in non-uniform strength and non-uniform heat treatment of the whole cloth manufactured using the activated carbon fiber. Further, when the total fineness of the activated carbon fiber is less than 300 denier, productivity is low, thereby reducing economic feasibility, and when the total fineness is more than 30,000 denier, the weight is increased, thus making it impossible to weave whole cloth including the low-weight activated carbon fiber. That is, considering that the weight of whole cloth including typically used activated carbon fiber is 50 to 300 g/m², when the total fineness is less than 300 denier, the number of yarn strands that are required during weaving and knitting is very high, and accordingly, processability is difficult. When the total fineness is 30000 denier or more, an appropriate whole-cloth design is not obtained. Further, the density is very low, thus reducing the stability of whole cloth.

In the present invention, the activated carbon fiber may have a strength of 0.01 to 1.0 g/denier.

Typically, when the precursor fiber for the activated carbon fiber is activated, the weight is reduced by about 50 to 90% during the flame-retardant and carbonization process, and oxygen (O), nitrogen (N), and hydrogen (H), which are residual components other than carbon (C), are decomposed, thereby reducing the weight and forming micro-pores.

However, when the filament-type precursor fiber is used as in the present invention, tension is applied in horizontal-axis and vertical-axis directions. Therefore, the shrinkage of the precursor fiber is lower than that of the staple fiber, and the reduction in yarn strength of the precursor fiber after activation is reduced. Accordingly, the resultant strength of the ultimately manufactured activated carbon fiber may be 0.01 to 1.0 g/denier.

A method of manufacturing an activated carbon fiber according to the present invention includes (S1) stabilizing a filament-type precursor fiber, and (S2) activating the filament-type precursor fiber by carbonizing the stabilized filament-type precursor fiber in an inactive atmosphere.

In the present invention, the method may further include precipitating the filament-type precursor fiber in an alkali solution before step (S1) when the filament-type precursor fiber is a cellulose-based filament-type precursor fiber or an aramid-based filament-type precursor fiber.

Further, in the present invention, the method may further include drying the filament-type precursor fiber before step (S1) when the filament-type precursor fiber is a polyacrylonitrile-based filament-type precursor fiber. Further, the method may further include precipitating the filament-type precursor fiber in the alkali solution before the drying.

[Precipitating the Filament-Type Precursor Fiber in the Alkali Solution]

The filament-type precursor fiber may be precipitated in the alkali solution in order to further improve the strength and the yield of the activated carbon fiber. The filament-type precursor fiber may be selected from the group consisting of a cellulose-based filament-type precursor fiber, a polyacrylonitrile-based filament-type precursor fiber, and an aramid-based filament-type precursor fiber.

The alkali solution may be selected from the group consisting of a phosphoric acid aqueous solution, an ammonium phosphate aqueous solution, and a zinc chloride aqueous solution, but is not limited thereto. The alkali solution may have a concentration of 5 to 20%. The filament-type precursor fiber may be precipitated in the alkali solution at the aforementioned concentration, thereby further improving the strength and the yield of the final activated carbon fiber.

[Drying the Filament-Type Precursor Fiber]

When the filament-type precursor fiber is dried, the filament-type precursor fiber may be a polyacrylonitrile-based filament-type precursor fiber.

The drying may be performed using heat treatment at a temperature of 100 to 150° C., and the heat treatment temperature for drying is set so as to minimize the reduction in weight of the precursor fiber. Examples of the drying may include hot-wind drying and drying using a high-temperature roller. When the high-temperature roller is used, the heat-transfer efficiency is typically favorable, and accordingly, drying treatment may be performed at relatively low temperatures in a short time compared to the case of hot-wind drying.

[Step (S1)]

Step (S1) includes stabilizing the filament-type precursor fiber.

The filament-type precursor fiber may be selected from the group consisting of a cellulose-based filament-type precursor fiber, a polyacrylonitrile-based filament-type precursor fiber, and an aramid-based filament-type precursor fiber.

The filament-type precursor fiber may be stabilized using heat treatment, which adopts hot wind or a high-temperature roller, in an inactive gas atmosphere, such as nitrogen (N₂), at a temperature of 200 to 350° C. for 10 to 240 min when the filament-type precursor fiber is a cellulose-based filament-type precursor fiber or an aramid-based filament-type precursor fiber. The filament-type precursor fiber may be stabilized using heat treatment in ambient air at a temperature of 200 to 300° C. for 30 to 240 min when the filament-type precursor fiber is a polyacrylonitrile-based filament-type precursor fiber. The stabilization temperature and time are set in consideration of the optimum stabilization effect.

[Step (S2)]

Step (S2) includes activating the stabilized filament-type precursor fiber.

The filament-type precursor fiber may be activated at a temperature of 650 to 1,050° C. after low-temperature carbonization in an inactive atmosphere at a temperature of 300 to 500° C. for 1 to 30 min when the filament-type precursor fiber is the cellulose-based filament-type precursor fiber or the aramid-based filament-type precursor fiber. The filament-type precursor fiber may be activated at a temperature of 650 to 1,050° C. after high-temperature carbonization in an inactive atmosphere at a temperature of 500 to 950° C. for 1 to 30 min when the filament-type precursor fiber is the polyacrylonitrile-based filament-type precursor fiber.

After the filament-type precursor fiber is carbonized, steam (H₂O), carbon dioxide (CO₂), oxygen (O₂), or ammonia (NH₃) may be added in an amount of 5 to 35% to a nitrogen (N₂) atmosphere at a temperature of 650 to 1,050° C., depending on the specific surface area (BET), to thus activate the filament-type precursor fiber. Steam (H₂O) and carbon dioxide (CO₂) may be typically used.

Durability and uniform adsorption ability may be ensured only when thermal decomposition is performed while the temperature is slowly increased during the aforementioned carbonization time.

Further, carbonization may be performed in an inactive atmosphere such as N₂, and activation may be performed using CO₂ or steam to form micro-pores in the surface of the activated carbon fiber precursor. The ability to form the micro-pores is excellent when CO₂ is used, but it is preferable to use steam in view of improvement of the specific surface area.

Further, the present invention relates to a woven fabric or a knitted fabric which is manufactured using the activated carbon fiber. In order to impart the woven fabric or the knitted fabric, which is manufactured using the activated carbon fiber, to have appropriate durability, as described above, the strength of the activated carbon fiber may be 0.01 to 1.0 g/de, and the weight of the woven fabric or the knitted fabric may be 10 to 600 g/m². When the weight of the woven fabric or the knitted fabric is less than 10 g/m², the woven fabric or the knitted fabric forms a very light thin film, and accordingly, the desired durability is not ensured. When the weight is more than 600 g/m², heat treatment may not be uniformly performed during the flame-retardant and activation process, resulting in partial BET and the non-uniformity of physical properties. Therefore, the weight of the woven fabric or the knitted fabric may preferably be 20 to 500 g/m².

MODE FOR INVENTION

A better understanding of the present invention may be obtained through the following examples which are set forth to illustrate, but are not to be construed to limit the present invention. Furthermore those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Examples 1 and 2

Whole cloth having a weight of 300 g/m² was woven using the precursor fiber for activated carbon, which is shown in Table 1. For the structure of the whole cloth, 2/2 twill was applied. The manufactured whole cloth was precipitated in a 10% phosphoric acid (H₃PO₄) aqueous solution and then dried using hot wind at 120° C. for 40 min. The dried whole cloth was carbonized in an inactive atmosphere (N₂) at 220 to 300° C. for 20 min and then activated using steam in an activation furnace at a temperature of 650 to 950° C. for 20 min to manufacture an activated carbon fiber.

Example 3

A 3600-denier PAN-based precursor fiber having 3000 filaments was woven using the same procedure as Examples 1 and 2 so as to have the same structure as Examples 1 and 2. The woven substance was subjected to flame-retardant treatment in ambient air at 230° C. for 4 hours without chemical-precipitation treatment, and then was carbonized in an inactive atmosphere while the temperature was increased to 450 to 800° C. for 5 min. The manufactured sample was activated using steam in an activation furnace at 950° C. for 20 min to manufacture an activated carbon fiber.

Example 4

A 3600-denier aramid-based precursor fiber having 3000 filaments was woven using the same procedure as in Examples 1 and 2 so as to have the same structure as in Examples 1 and 2, precipitated in a 10% phosphoric acid (H₃PO₄) aqueous solution, and dried using hot wind at 120° C. for 40 min. The dried substance was carbonized in an inactive atmosphere (N₂) at 220 to 300° C. for 20 min, and was then activated using steam in an activation furnace at a temperature of 650 to 950° C. for 20 min to manufacture an activated carbon fiber.

Comparative Examples 1 and 2

An activated carbon fiber was manufactured using the same procedure as in Example 1, except that the precursor fiber for activated carbon shown in Table 1 was used.

TABLE 1 Precursor fiber for activated carbon Single-yarn Total Strength fineness fineness Activation Name (g/denier) (denier) (denier) yield (%) Example 1 Viscous rayon-based 3.2 1.8 300 17 filament-type precursor fiber Example 2 Lyocell-based filament- 5.8 1.6 1500 23 type precursor fiber Example 3 PAN-based filament-type 8.0 1.2 3600 42 precursor fiber Example 4 Aramid-based filament- 25 1.2 1500 32 type precursor fiber Comparative Cotton short fiber — — 450 15 Example 1 precursor fiber Comparative Viscous rayon staple 2.1 2.2 300 11 Example 2 precursor fiber for clothes

The strength of the activated carbon fibers, which were manufactured in the Examples and the Comparative Examples, was measured using the following method.

(1) Strength

The strength of the precursor fiber and the activated carbon fiber was measured according to KS K0412.

TABLE 2 Strength of activated carbon fiber Example 1 0.04 Example 2 0.25 Example 3 0.31 Example 4 0.71 Comparative Example 1 0.01 or less Comparative Example 2 0.01 or less

From the results of measurement of physical properties thereof, it can be confirmed that the strength is lower in Comparative Examples 1 and 2, in which the activated carbon fiber is manufactured using a short fiber or a staple precursor fiber, than in the Examples, in which the activated carbon fiber is manufactured using the filament-type precursor fiber.

Meanwhile, for the pitch-based and phenolic short fibers, which are not described in the Examples of the present invention, the yield and durability are very low, and accordingly, it is very difficult to check the physical properties of the pitch-based and phenolic short fibers. 

1. A filament-type activated carbon fiber that is manufactured by activating a filament-type precursor fiber for the activated carbon fiber and has a strength of 0.01 to 1.0 g/denier.
 2. The filament-type activated carbon fiber of claim 1, wherein the filament-type precursor fiber for the activated carbon fiber is selected from the group consisting of a cellulose-based filament-type precursor fiber, a polyacrylonitrile-based filament-type precursor fiber, and an aramid-based filament-type precursor fiber.
 3. The filament-type activated carbon fiber of claim 1, wherein the filament-type precursor fiber has a strength of 5 to 12 g/denier.
 4. The filament-type activated carbon fiber of claim 1, wherein the filament-type precursor fiber has a single-yarn fineness of 0.05 to 10 denier and a total fineness of 300 to 30,000 denier.
 5. A method of manufacturing an activated carbon fiber, the method comprising: (S1) stabilizing a filament-type precursor fiber; and (S2) activating the filament-type precursor fiber by carbonizing the stabilized filament-type precursor fiber in an inactive atmosphere.
 6. The method of claim 5, further comprising: precipitating the filament-type precursor fiber in an alkali solution before step (S1).
 7. The method of claim 6, wherein the filament-type precursor fiber is a cellulose-based filament-type precursor fiber or an aramid-based filament-type precursor fiber.
 8. The method of claim 5, further comprising: drying the filament-type precursor fiber before step (S1).
 9. The method of claim 8, further comprising: precipitating the filament-type precursor fiber in an alkali solution before the drying.
 10. The method of claim 8, wherein the filament-type precursor fiber is a polyacrylonitrile-based filament-type precursor fiber.
 11. The method of claim 5, wherein the stabilizing of step (S1) is performed using heat treatment in the inactive atmosphere at a temperature of 200 to 350° C. for 10 to 240 min when the filament-type precursor fiber is a cellulose-based filament-type precursor fiber or an aramid-based filament-type precursor fiber, and using heat treatment in ambient air at a temperature of 200 to 300° C. for 30 to 240 min when the filament-type precursor fiber is a polyacrylonitrile-based filament-type precursor fiber.
 12. The method of claim 5, wherein the activating of step (S2) is performed at a temperature of 650 to 1,050° C. after low-temperature carbonization in the inactive atmosphere at a temperature of 300 to 500° C. for 1 to 30 min when the filament-type precursor fiber is a cellulose-based filament-type precursor fiber or an aramid-based filament-type precursor fiber, and at the temperature of 650 to 1,050° C. after high-temperature carbonization in the inactive atmosphere at a temperature of 500 to 950° C. for 1 to 30 min when the filament-type precursor fiber is a polyacrylonitrile-based filament-type precursor fiber.
 13. The method of claim 6, wherein the alkali solution is selected from the group consisting of a phosphoric acid aqueous solution, an ammonium phosphate aqueous solution, and a zinc chloride aqueous solution.
 14. The method of claim 8, wherein the drying is performed using heat treatment at a temperature of 100 to 150° C.
 15. A woven fabric manufactured using the activated carbon fiber of claim
 1. 16. A knitted fabric manufactured using the activated carbon fiber of claim
 1. 17. The method of claim 9, wherein the alkali solution is selected from the group consisting of a phosphoric acid aqueous solution, an ammonium phosphate aqueous solution, and a zinc chloride aqueous solution. 